The present invention relates to a removable cap with a fluid passage for an elongated instrument. More particularly, the removable cap of the invention is used for a writing instrument and includes an air passage therein.
An elongated or writing instrument, such as a ball point pen and a marker, generally includes a cap for closing a tip of the writing instrument when it is not used. When the writing instrument is used, the cap is detached from the writing instrument. The detached cap may be put on a back end of the writing instrument, or placed on a desk or some other places. After using the writing instrument, the detached cap will be returned to cover the tip of the writing instrument, but the cap may be left as it is.
No matter if the cap is left alone or attached to a writing instrument, when a child or infant plays with the writing instrument or cap, the cap may be swallowed to thereby chock the throat. This kind of accident happens many times.
In order to prevent choking when the cap is swallowed, a hole penetrating through the cap may be formed. However, when the cap is properly fixed to the writing instrument, the cap must close the tip of the writing instrument completely to prevent evaporation of an ink of the writing instrument. The cap must have two contradictory functions therein.
In view of the above situation, there have been proposed many removable caps to provide air passages therein while completely closing the tip of the writing instrument when attached to the writing instrument.
In U.S. Pat. No. 4,915,529, a separate air channel is formed inside a cap while adding a partition in the cap.
In U.S. Pat. Nos. 5,061,105 and 5,427,464, a cap is formed of inner and outer shells. The inner shell completely closes the tip Of the writing instrument, while an air channel is established between the inner and outer shells.
In U.S. Pat. No. Des. 335,146 and U.S. Pat. No. 5,316,402, a plurality of ribs is formed on an outer surface of the cap to establish an air passage between the ribs.
In the prior art patents, an air passage is formed even if the cap is swallowed. However, in case the partition or inner shell is formed, the structure of the cap becomes complicated. On the other hand, if the ribs are formed on the outer surface of the cap, the appearance of the cap is impaired.
Accordingly, one object of the invention is to provide a removable cap with a fluid passage for an elongated or writing instrument, which has a simple structure to establish the fluid passage.
Another object of the invention is to provide a removable cap as stated above, which can be easily and economically manufactured.
A further object of the invention is to provide a removable cap as stated above, which does not impair appearance of the cap.
Further objects and advantages of the invention will be apparent from the following description of the invention.